1. Field of the Invention
The present invention relates to automated process control systems, and in particular, to a user interactive process control system which is rapidly expandable and adaptable for use in many different types of processes.
2. The Prior Art
Over the years, process controls systems have evolved from relatively simple individual controllers for specific process conditions to very large integrated systems including digital processing equipment. In order to obtain process information from these systems quickly, for use by the operators, large control panels were often required often, complex control systems may have control panels which are several feet in length, with the process information and operator control devices located at various places along the panel.
Arrangements in which the information and control devices are spread out in such a manner have serious drawbacks. As a result, efforts have been made to more effectively consolidate the information and controls However, the costs for obtaining reliability and speed, as well as the operating and maintenance expenses have continued to be a concern in such complex systems. This results from the fact that conventional process controllers typically require hundreds of input/output wires. Further, to obtain machine-controller integration of a process and control system typically requires a design and installation process taking weeks of skilled labor to complete.
The numerous electro-mechanical connections involved in the complex systems are common sources of failure which produce a high maintenance expense. This expense not only arises due to failures within the central control system itself, but it also arises in connection with failures of remote actuators or sensing equipment, and controllers associated with that sensing equipment. The reason for this is that when failures occur at these remote locations, or in lines connecting the remote locations, prior art systems have typically not provided any means for quickly identifying the location of the failure. As a result, a significant portion of the repair costs arise from time spent in discovering the location of the failure.
The start-up of a typical prior art programmable control system requires many time-consuming procedures such as component selection, design of the operator's panel, purchase and modification of the cabinetry, wiring design with hundreds of connections, and extensive hardware testing and debugging. The design and construction of such systems is generally based on anticipated use of the system in connection with a specified application. Thus, the system is generally not easily adapted for applications other than those originally contemplated. Further, these complex prior art systems generally require extensive rewiring and hardware modification if they are to be expanded in their operations, or adapted for other uses. For example, in a typical expansion of a control system, further input/output connections must be added, with wires being pulled through conduit. The operator's panel must be redesigned and documented, and the software modified. Further, for many systems, it is impossible to adapt the monitoring portion of the system for other applications, and only the central controller can be reused for new applications.
In light of the above, it will be appreciated that it would be an important improvement in the technology to provide a process control system which would adapt easily to a variety of applications, and which would readily permit expansion of the system so that it may grow with the process being controlled, without excessive costs for accomplishing the expansion. Such a system would advantageously include sensing and control modules located remotely from the central control unit and capable of independent diagnosis of the status and operation of its associated controlled process devices, and the capability of a priority communication system to rapidly communicate fault or error conditions to the user via the control unit. It would be a still further improvement in the art to provide such a system which would require a minimum amount of wiring and electrical connections both in the controller as well as in connection with the remote sensing devices.
It would also be an important improvement in the technology to provide such a system which could consolidate information and control operations in a single display arrangement available for an individual user, and provide for simplified operation of the system by use of the interactive control arrangement. Still a further improvement in the art would be provided by a built-in diagnostic capability which would identify the location of hard failures, and which would identify intermittent-fault conditions in order to permit preventive maintenance to be scheduled during normal down time. Still a further improvement in the system would be provided by including in such a system the capability of presenting a check list of corrective procedures in order to overcome a given failure situation.